The present invention relates to compositions suitable for use as particulates in subterranean operations, such as proppant or gravel. More particularly, the present invention relates to composite particulates comprising a base material and a nanoparticle material.
Particulates are used in a variety of operations and treatments performed in oil and gas wells. Such operations and treatments include, but are not limited to, production stimulation operations such as fracturing, well completion operations such as gravel packing, and combined operations such as frac-packing.
An example of a production stimulation operation using a servicing fluid having particles suspended therein is hydraulic fracturing, wherein a servicing fluid known as a fracturing fluid is pumped through a well bore into a portion of a subterranean formation at a rate and pressure such that fractures are formed and/or enhanced into the subterranean zone. The fracture or fractures may range from horizontal to vertical, with the latter usually predominating, and with the tendency toward vertical fracture orientation with the depth of the formation being fractured. A suitable fracturing fluid is generally a viscosified treatment fluid, emulsion, or foam that may comprise a particulate material often referred to as proppant. Proppant may be deposited in a fracture and function, inter alia, to hold the fracture open while maintaining conductive channels through which produced fluids can flow upon completion of the fracturing treatment and release of the attendant hydraulic pressure.
An example of a well completion operation using a servicing fluid containing particulates is gravel packing. Gravel packing treatments are used, inter alia, to reduce the migration of unconsolidated formation particulates into the well bore. In gravel packing operations, particles referred to in the art as gravel are carried to a well bore in a portion of a subterranean formation by a hydrocarbon or water-based carrier fluid. That is, the particulates are suspended in a carrier fluid, which may be viscosified, and the carrier fluid is pumped into a well bore in which the gravel pack is to be placed. As the particulates are placed in the zone, the carrier fluid leaks off into the subterranean zone and/or may be returned to the surface after passing through a screen positioned adjacent to the productive interval. The resultant gravel pack acts as a filter to separate formation solids from produced fluids while permitting the produced fluids to flow into and through the well bore. Traditional gravel pack operations involve placing a gravel pack screen in the well bore and packing the surrounding annulus between the screen and the well bore with gravel sized to prevent the passage of formation particulates through the pack with produced fluids. The gravel pack screen is generally a filter assembly used to support and retain the gravel placed during the gravel pack operation. A wide range of sizes and screen configurations are available to suit the characteristics of a well bore, the production fluid, and any particulates in the subterranean formation. Gravel packs may be used to stabilize a portion of a formation while causing minimal impairment to well productivity. The gravel, inter alia, acts to prevent the particulates from occluding the screen or migrating with the produced fluids, and the screen, inter alia, acts to prevent the gravel from entering the well bore.
In some situations the processes of hydraulic fracturing and gravel packing are combined into a single treatment to provide a stimulated production and an annular gravel pack to prevent formation sand production. Such treatments are often referred to as “frac pack” operations. These treatments are often completed with a gravel pack screen assembly in place with the hydraulic fracturing treatment being pumped through the annular space between the casing/open hole and screen. In this situation the hydraulic fracturing treatment is typically designed to screen out at the fracture tip, creating a packed fracture and an annular gravel pack between the screen and casing/open hole. This allows both the hydraulic fracturing treatment and gravel pack to be placed in a single operation. In other cases the fracturing treatment may be performed prior to installing the screen and placing a gravel pack.
Servicing fluids such as fracturing fluids, gravel packing carrier fluids, and frac pack fluids, generally must be highly viscous to be able to adequately suspend particulates so as to be able to place them in a desired location. To achieve a high viscosity, viscosifiers often are added to such fluids. Such viscosifiers are often expensive. Moreover, as a fracture or a gravel pack is created a portion of the liquid contained in the fluid may leak off into the formation and create a filter cake comprising deposited viscosifier on the walls of the fracture, well bore, and/or the formation, which may be undesirable.
The particulates used in subterranean application should have a high enough strength to withstand various forces within the formation, yet they should be relatively lightweight so that a servicing fluids used to carry them may need a reduced amount of viscosifier.